1) A spring is stretched by an initial amount from its relaxed state. If the spring is then stretched by nine times that amount from its relaxed state, by what factor does the amount of mechanical energy stored in the spring change?

2) Two persons on ice skates stand face to face and then push each other away. Their masses are 65 and 90 kg. a. Find the ratio of their speeds immediately afterward. b. Which person has the higher speed?

3) A worker at the top of a 504-m-tall television transmitting tower accidentally drops a heavy tool. If air resistance is negligible, how fast (in m/s) is the tool going just before it hits the ground? _____m/s

4) A student drops a water balloon out of a dorm window 28 m above the ground. What is its speed when it hits the ground? _____m/s

5) The cliff divers at Acapulco, Mexico, jump off a cliff 21.7 m above the ocean. Ignoring air resistance, how fast are the divers going when they hit the water? ___m/s

6) A bicycle and rider going 13 m/s approach a hill. Their total mass is 54 kg. (a) What is their kinetic energy? (b) If the rider coasts up the hill without pedaling, how high above its starting level will the bicycle be when it finally rolls to a stop?

7) The ceiling of an arena is 27 m above the floor. What is the minimum speed that a thrown ball would need to just reach the ceiling? ___m/s

8) Three objects are set in motion, a 4.6 kg object at 2.2 m/s, a 3.4 kg object at 3.4 m/s, and a 2.2 kg object at 4.6 m/s. Which object has the most kinetic energy?

a. the 4.6 kg object at 2.2 m/s

b. the 3.4 kg object at 3.4 m/s

c. the 2.2 kg object at 4.6 m/s

d. Since the mass and velocity add together to 6.8 in each case, the kinetic energy for each object is the same.

9) A force applied to a spring compresses the spring 13 cm, storing a certain amount of elastic potential energy. Then a larger force is applied to compress the spring a total of 78 cm. How does the elastic potential energy stored in the spring after it is compressed 78 cm compare to the elastic potential energy stored in the spring after it was compressed 13 cm?

a. The elastic energy stored in the spring when compressed 78 cm isthe sameas when it is compressed 13 cm.

b. The elastic energy stored in the spring when compressed 78 cm issix times as muchas when the spring is compressed 13 cm.

c. The elastic energy stored in the spring when compressed 78 cm isthirty-six times as muchas when the spring is compressed 13 cm.